| Summary: The aim of the thesis study is to examine brightness effect, which is the perceptual property of visual stimuli, on the brain activity that occurs during the visual processing of these stimuli. In this study, responses of the brain to changes in brightness of image was investigated comparatively using different emotional images (pleasant, unpleasant and neutral) with different luminance levels (original and bright). The research was carried out using both statistical and classification methods. Electroencephalography (EEG) records of 14 different electrode regions of 31 healthy participants were used in this study. Power spectrograms of EEG recordings were obtained with short-time Fourier transform. The features extracted from these spectrograms were compared with statistical methods between the original and bright groups for three different emotional contents. Statistical findings revealed that the brightness of visual stimuli varies the power of brain responses depending on frequency, time, electrode point and image content. After all these processes, the features obtained from the original and bright groups for pleasant, unpleasant and neutral images were classified between the two groups. The classification results revealed that the features obtained for the original and bright versions of neutral, pleasant and unpleasant images can be separated by 71-81% accuracy using different classification methods. All results revealed that the brightness of the visual stimulus can be represented on the brain cortex by the change in power of activity. |
